I don't think it should have been paid from the start (I don't think it should be paid now either though... )
But going paid from the start would only have added to their disadvantages. I mean the PS3 launched nearly a year after the Xbox 360 and was significantly more expensive to boot. (Sort of inverse of what is happening now...)
Plus at the start there weren't many titles for PS3 because developers were still figuring out how to use the PS3's power.
So if they had gone with a paid service on top of the already expensive hardware I think a lot of people would have just gone with the initially cheaper 360. (Since the free online was an incentive to pick PS3.)
In terms of being paid, I don't think it will really help that much. I mean
xbox live was still hacked into (despite the fact they are paid). And no amount of money is going to be able to protect you from a group of really determined hackers. They're going to get in somehow. So even if they were completely paid at the time of the PSN hacks, the likelihood is that it wouldn't have helped. The only thing is that they'd have to do more reimbursing.
People seem to think that just because you pay for something that you're getting better quality. But the problem is that isn't always true. Some things that are paid are shit. But since someone paid for them, they don't want to admit it was shit. (Because then they'd have to admit they wasted their money.)
Furthermore, just because something goes from free to paid doesn't mean that quality will improve. And in this case, all Sony has done is moved online play from the free side to behind the paywall. (Pulling a microsoft move.)
And even when PSN does go paid, it won't fix anything if your connection to Sony's servers isn't very good. (If that's why you had troubles on PSN before, that's not likely to improve since it's a connection issue from your ISP to Sony's servers. Might have nothing to do with Sony at all, but rather your ISP.)
Plus I highly doubt that even when PSN is paid things will really improve much. I imagine things will stay pretty much like they are now simply because Sony won't have to do anything to improve. They're at a comfortable place with plenty of good PR (going against a company who's PR is pretty bad now and really not improving very much). So there really isn't any incentive for them to improve. Especially since, once you pay, they already have your money.
And regarding PSN vs XBL... I used to see a lot of people say XBL was so much better (I don't see that line trotted out much anymore), but not a single one of them could ever offer an actual reason for it. They always only ever said shit like: "because it's paid" or "because it is". (Those aren't reasons... those are your opinions. Two very different things. If you want to make claims something is uniformly better then you need to provide some very good reasons/evidence for it.)